The disclosed technology relates to corrosion- or rust-preventive coating compositions and methods of their use. The compositions comprise a higher and a lower melting triglceride (which may be one or more hydrogenated natural oils) and a solubility agent, optionally in a hydrocarbon medium.
Rust preventive coatings have been known to comprise a mineral (hydrocarbon) wax in a solvent or other liquid medium. Such coatings have been applied to metal surfaces, especially ferrous surfaces, as a rust preventative. They may be distinguished from other types of coatings such as paints in that the wax-containing coatings are often of a relatively temporary nature, imparting rust inhibition over a term of days or perhaps years, and in some instances being removed prior to further treatment of or working with the metal surface.
Coating and anti-rust compositions are known. For instance, WO 2013/134062, Lubrizol, Sep. 12, 2013, discloses waterborne coatings that provide improved corrosion protection. The composition may include water, a polymer resin component, and a corrosion inhibiting component comprising a first complexing agent comprising a trialkanol amine and a second complexing agent comprising a carboxylic acid.
U.S. Pat. No. 5,074,913, Trivett, Dec. 24, 1991, discloses hot melt pipe coating compositions. One disclosed formulation comprises 10% by weight of the triglyceride of 12-hydroxystearic acid, 25% by weight of polymerized aliphatic terpene hydrocarbon resin, 44% by weight ethylene copolymer, 20% by weight synthetic paraffin wax, and 1% by weight antioxidant.
U.S. Pat. No. 7,737,099, Applewhite et al., Jun. 15, 2010, discloses compositions and methods for the prevention and treatment of corrosive processes such as rust. The compositions may include an organic acid or salt, a natural gum and/or wax and/or wax extract, and water.
U.S. Pat. No. 8,409,340, Kharshan et al., Apr. 2, 2013, discloses bio-based corrosion inhibitors, e.g., “distillers dried grains with solubles” extract, which was analyzed to contain 16 and 18 carbon fatty acids and ethyl esters, among other components.
GB 1 249 144, Esso Research and Engineering Company, Oct. 6, 1971, discloses an organic rust inhibiting composition comprising an aqueous ammonia gelled overbased alkaline earth metal sulfonate, a coating material which is a hydrocarbon polymer resin or a mixture of a hydrocarbon polymer resin, wax, and ethylene-vinyl acetate copolymer, and a hydrocarbon solvent.
U.S. Pat. No. 6,312,509, Moradian, Nov. 6, 2001, discloses a rust preventive coating composition including a microcrystalline wax, naphthenic and paraffinic oils, oils-soluble alkali-metal sulfonate, or other components.
U.S. Pat. No. 4,946,503, Hattori et al., discloses a rust preventive coating composition comprising asphalt, metallic salt of petroleum sulfonic acid, metallic salt of petrolatum oxide, wax-like material, microwax, and other components.
EP 1 038 933, Kawasaki Steel Corporation, Sep. 7, 2000, discloses a coating composition comprising a methacrylic resin prepared by copolymerizing styrene or a substituted styrene, a methacrylic ester, and an olefinic compound having at least one carboxylic group.
Ester-containing polymers are also known. WO 96/07720, Exxon Chemical Patents, Mar. 14, 1996, discloses compositions comprising an ethylene/vinyl acetate or propionate/vinyl linear carboxylate terpolymer. In an example, a polymer is prepared from vinyl octanoate, vinyl acetate, and ethylene. They are useful for improving the low-temperature properties of certain oils. WO 99/62973, Infineum USA, Dec. 9, 1999, discloses copolymers formed from dialkyl phenyl fumarate and at least one comonomers formed form the group consisting of vinyl acetate, styrene, C3 to C30 α olefin, ethylene, and carbon monoxide. In an example, copolymers of dialkyl phenyl fumarate with vinyl acetate were synthesized with R groups of C12H25, C24-28H49-57, C30H61. U.S. Pat. No. 6,017,370, Manka et al., Jan. 25, 2000, discloses a liquid composition containing a polymer of a C8-10 alkyl ester of an ethylenically unsaturated 1,2-diacid.
It would be desirable obtain alternative waxes from sustainable, renewable sources, at a relatively low cost, and which provide very good rust inhibiting performance, including good film integrity and few premature failures.
A possible source of alternative waxes is natural (renewable) products such as animal or vegetable oils or fats (waxes). Animal and vegetable oils and fats are triglycerides of fatty acids of various types, the specific acid depending on the source of the oil. Often different fatty acid components are present within a single triglyceride molecule, and the specific mixtures and combinations will affect the nature of the oil or fat. The triglycerides will be characterized as oil or waxes (fats) generally on the basis of whether they are liquid a room temperature (oils) or solid or semi-solid at room temperature (fats or waxes). Chemically, triglycerides that contain alkyl chains containing unsaturation are typically classified as oils, while fats or waxes often contain saturated or more nearly completely saturated alkyl chains. The waxes would be expected to be more suitable than oils in anti-rust coating compositions, because their higher melting points will make them more likely to remain on the metal surface, rather than being removed by natural flow or by contact with other materials.
Triglyceride oils may be converted into waxes by partial or complete hydrogenation of one or more of the double bond or bonds in the alkyl chains. Since such waxes are readily available, they would be possible candidates for use in rust preventive coatings. However, a problem arises because of generally inadequate solubility of triglyceride waxes in solvents that are typically used in preparing or applying rust preventive compositions. Poor solubility can lead to precipitate formation in the final coating product and poor corrosion protection.
The disclosed technology, therefore, solves one or more of the problems of providing a wax from a natural source rather than a hydrocarbon wax; and providing a composition which exhibits good solubility in oils or volatile solvents while simultaneously providing good rust or corrosion inhibition to a metallic surface to which it is applied.